fix: #3622846 Match the email field height on themes with taller buttons

Fixes #3622846.

What this changes

#3622822 gave the email input and the Subscribe button the same explicit minimum height. That lines them up on Horizon Aid. It does not line them up on a theme whose button computes taller than the floor, because a floor is a minimum: any button above it reopens the gap by exactly that difference.

Measured on Educare at 1440px, with #3622822 in place:

	height
email input	56px (the floor)
Subscribe	58px (theme button padding)

One line fixes it:

'#attributes':
  class:
    - w-100
    - h-100
    - rounded-pill
    - px-4
  style: 'min-height:3.5rem'

Why both, and not one or the other

They cover different cases, and neither is sufficient alone.

• Wide screen: the row is a flex row with align-items-stretch, so the email wrapper is already stretched to the button's height. h-100 makes the input fill it, whatever that height turns out to be.
• Narrow screen: the row becomes a column, the cross axis is width, and h-100 does nothing. The minimum height is what keeps the input above the 44px touch target.

h-100 alone was tried first in #3622822 and rejected for exactly that reason. This adds it back alongside the floor rather than instead of it.

Verification

Measured in a browser, anonymously, with both present:

Site	1440px	390px
Educare	58 / 58	56 / 56
Horizon Aid	56 / 56	56 / 56

Top-aligned in every case, and no regression on Horizon Aid, where the floor already matched.

Checkpoints:

• File an issue
• Addition/Change/Update/Fix
• Testing to ensure no regression
• Automated unit testing coverage
• Automated functional testing coverage
• UX/UI designer responsibilities
• Readability
• Accessibility
• Performance
• Security
• Developer Documentation
• User Guide Documentation
• Reviewed by human
• Code review by maintainers
• Full testing and approval
• Credit contributors
• Review with the product owner
• Release notes snippet
• Release

AI-Generated: Yes